FORMATION OF THE INTERMEDIATE, AQUOHYDROXOBIS (ETHYLENEDIAMINE)COBALT(III) COMPLEX, IN THE PREPARATION OFCIS-BROMOAMMINEBIS (ETHYLENEDIAMINE)COBALT(III) BROMIDE BY THE REACTION OF BIS[BIS(ETHYLENEDIAMINE)COBALT(III)-μ-DIHYDROXO]DIAQUOCOBALT(II) SULFATE WITH AMMONIUM BROMIDE IN WATER

The production of cis-[CoBr(NH3)(en)2]Br2 by reaction of [Co(H2O)2{(OH)2Co(en)2}2](SO4)2 with ammonium bromide in water was investigated. The reaction seems to proceed through the intermediate, [Co(H2O)(OH)(en)2]2+, and then convert to the product, cis-[CoBr(NH3)(en)2]2+. This is supported by the observation that the absorption spectrum of the reaction solution immediately after the disappearance of the starting complex was different from that of cis-[CoBr(NH3)(en)2]2+ but was quite similar to that of [Co(H2O)(OH)(en)2]2+. In order to confirm this reaction pathway, cis-[Co(H2O)(OH)(en)2]Br2 was prepared and reacted with ammonium bromide producing the expected complex, cis-[CoBr(NH3)(en)2]Br2.